I'm not familiar with cottonwood. I would start by asking if you scratch it with your fingernail does it leave a good scratch? Not crushed, just scratched. If so and the wood isn't an oily wood and it is well dried out it should work. Your board should be about 3/8" thick, and I like a spindle about 3/4" or so round. Make sure your bow is snug and not slipping. Also lube up your hand hold with something to keep friction to a minimum. I usually use juice from a leaf or some spit. You can use soap if you want a really smooth surface. When you make your notch that collects the dust make sure it extends into the center of the hole that the drill creates. Also make it wide enough that the dust doesn't collect around the hole but rather all fall into the notch. When you make the notch, the bottom should be wider than the top and it should extend deeper on the bottom than the top. That sounds confusing but it really helps to give the dust plenty of room to fall but keeps it warm and under cover. Once you have your set up dialed in, it now comes down to technique. Start off with nice smooth long stroke concentrating on form and breathing. People tend to hold their breath, this is a bad idea. Warm up the surfaces well with this method. Once you start getting some smoke, start increasing the speed and down pressure on your setup. Now once you think you have it.....KEEP GOING!!!!!!!!. Don't stop until you are 110% sure you have a coal. Keep trying, you will get it. Make sure you have a tinder bundle ready, because you will be really Pi$$ed if you get a coal and have no place for it. Hope this helps keep us posted on your progress. You should also give the hand drill a go. It is a bit harder physically, but much easier to get the technique down.